The present invention relates to curable organic resin compositions which employ a diaryliodonium-redox catalyst system of copper salt in combination with ascorbic acid, stannous salts or an activated .alpha.-hydroxy compound. More particularly, the present invention relates to organic resin foam and method of foaming.
As shown in my copending application Ser. No. 861,128, filed Dec. 16, 1977 and assigned to the same assignee as the present invention, aromatic iodonium salts can be employed in combination with organic acids or copper salts to facilitate the heat cure of various organic materials, such as epoxy resins. I have also found, as shown in my copending application Ser. No. 869,247, filed May 24, 1976, now abandoned, and assigned to the same assignee as the present invention, that valuable results also can be achieved if reducing agents such as thiophenol are used in combination with aryl onium salts to facilitate the thermal cure of epoxy resins. Surprisingly, in the absence of such cocatalysts, the cure of cationically polymerizable organic materials, such as epoxy resins, with an aromatic iodonium salt can require temperatures exceeding 200.degree. C. over a extended period of time. I have now discovered that if a diaryliodonium salt of the formula, EQU [(R).sub.a (R.sup.1).sub.b I].sup.+ [Y].sup.- (I)
is employed with a redox catalyst comprising a mixture of copper salt, ascorbic acid or derivatives thereof, an Sn.sup.+2 salt or an activated .alpha.-hydroxy compound with a cationically polymerizable organic material, e.g., an epoxy resin, the cure of the organic material can be achieved without the use of external heat, where R is a monovalent aromatic organic radical, R.sup.1 is a divalent aromatic organic radical, Y is a non-nucleophilic anion defined below, a is a whole number equal to 0 to 2, b is a whole number equal to 0 or 1, and when a is 0, b is 1, and when b is 0, a is 2. If an organic solvent is utilized with the cationically polymerizable organic material and the diaryliodonium salt-redox catalyst curing system, exothermic heat of reaction can generate an organic foam.